1. Field of the Invention
The present invention relates to an e-mail server.
2. Description of the Related Art
In recent years, under expansion of Internet, e-mail system is used broadly. Therefore, a user sometimes fills in his/her e-mail address as contact information in Internet shopping, user registration on Web, a survey on Web etc.
Such e-mail address filled in is usually managed as personal information so that the e-mail address is usually not leaked. However, it is occasionally leaked due to some causes, if leaked, SPAM mails for advertisement often come to the leaked e-mail address. In another case, a user may receive an e-mail virus from a friend if the friend's computer is infected with the virus. A sender (i.e. a sender's e-mail address) of a nuisance e-mail such as SPAM mail and e-mail virus is often disguised, and if it happens, it is difficult to identify the real sender and stop sending such nuisance e-mails.
For e-mail client programs sending/receiving e-mails, some techniques has been developed to discriminate and/or remove nuisance e-mails. In the techniques, an e-mail is received firstly, then it is determined whether the e-mail is a nuisance e-mail or not based on content of the e-mail. For example, such technique is described in Japanese Patent Application Laid-Open Gazette No. 2005-208780.